The ASTER Global DEM (GDEM) version 1, is a global digital elevation model with one arc-second grid, generated using the ASTER stereo image archive 2000 to August 2008, and was released on June 29, 2009. The GDEM-1 had some bad elevation data. The most simple and effective way to reduce bad elevation data in the GDEM-1 is to add new ASTER observation data and re-generate the GDEM. An ASTER Data Acquisition Request was defined, based on the number of good pixels and the number of observations at each observation area, for the GDEM version 2 that was released on October 17, 2011. Using more input data and an improved algorithm, GDEM version 2 reduced the amount of the bad pixel by 4.5% to 7.5% and increased the amount of good tiles by 10.7% to 54.3% over the GDEM-1, except for Antarctica. Another ASTER data set is being collected for GDEM version 3, scheduled for 2013. The ASTER data collection scheme, however, has some constraints. This study sought for techniques to optimize the GDEM data collection balancing the overall ASTER operations and reduction of bad pixels in the GDEM data.